Sherlock Holmes, Babysitter (by Consultation Only)
by Jesuslovesmarina
Summary: Wholock! Sherlock balances bottles, nappies, and sleep schedules with solving cases, hunting a Time Lord, and protecting his infant namesake from poisonous gas. Where have John and Mary been all this time?
1. Chapter 1

**A/N: I literally have no idea how this turned into a crossover. It was supposed to be about Sherlock having to babysit the Watson's baby for a while, and then I dropped in a cameo to make people squeal, and then I ended up making it a full-fledged Doctor Who crossover. Please enjoy and review! I do not own either of these fabulous shows.**

Sherlock Holmes, Babysitter (by Consultation Only)

Mary called and demanded him to babysit.

Mary _never_ asked him to babysit; in fact, when he had informed her that he was totally opposed to the idea of babysitting an eight-month-old, she had vehemently agreed that it would be a terrible idea, as had John.

So why she had called him in a frenzy, saying she was bringing Willie over in five minutes, was quite beyond his normal levels of deductive ability.

Was John ill? No, that was out of the question. John would never get ill when he had an eight-month-old living with him in the same house. Had Mary gotten called in to work, despite her extended maternity leave? She would have (metaphorically speaking) beaten her boss over the head with the phone and gone back to sleep. Was there some sort of overseas emergency? Had another of Mary's longtime enemies caught up with her again? Had John been called back to Afghanistan?

The impatient pounding on the door interrupted Sherlock's increasingly disturbing train of thought and he quickly rose from his chair to let Mary in, who was holding the chubby-faced baby girl on her hip.

"Thank you so much, Sherlock. It's a bit of an emergency and I don't have time to explain," she paused to catch her breath, and Sherlock could tell that she had not only sprinted up the stairs but was also incredibly nervous, as she was breathing very hard. "John and I've met this really strange person and we have to go immediately!"

She shoved the baby toward him and his long white fingers closed awkwardly around her midsection as she turned around quickly and began to disentangle herself from the diaper bag.

He looked Willie up and down before starting to realize his previous concerns hadn't been understated. "Who did you say you met?"

He really had no idea what he was doing. He couldn't keep holding her out in front of him like this for several hours, could he?

"It's pretty easy, Sherlock. Bottle every three hours and a nap every four!"

She threw down the diaper bag, dashed down the steps—and was gone.

A look of alarm crossed Sherlock's face. "But what if they coincide?" he exclaimed, trying to follow her, but afraid he would drop the baby if he moved too quickly. "Mary, come back!"

The door slammed at the bottom of the stairs.

 _Too late._

Sherlock tried not to panic. He looked back from the steps to the child, to the steps, back to the child, down at the diaper bag, and took a very large, deep breath.

He was clever. No, he was VERY clever. He could do this.

"Mrs. Hudson?!"

No answer.

"Mrs. Hudson, you know how you were moaning to me the other day that you hadn't held a baby in a while? I might possibly have a solution…"

What had she had said earlier? Oh, right.

Her sister was in town and they would be out shopping and to the theater.

In a scenario in which he interrupted their film with a squalling child, just how upset would they be?

Speaking of squalling, however, Willie didn't look too happy about being suspended in midair. She started to fuss, and Sherlock attempted to settle her across his chest so he could move, clinging to her with both hands like his parents had taught him to hold breakable objects when he was little.

His laptop was sitting on the desk ten feet away. All he had to do was make it over there.

One step, two ste—

And in spite of the dense network of experimental objects and knickknacks scattered precariously across the floor, Sherlock tripped over the rug.

He gasped and barely caught himself before he landed right on top of the child, squashing her into rug-Willie-and-Sherlock soup. In doing so, however, he jostled her in his arms and had to let go with one arm, and she began crying in earnest.

"Oh—um, hush—it's okay," Sherlock hummed nervously, trying to stand up. Willie's head flopped backward, unsupported, and he cringed as he rotated her into a better position. Babies were so _tremendously_ delicate! Why did they have to make them this way?

Meticulously, he picked his way through the mess on the floor and landed, with a sigh of relief, on the chair in front of his computer. Glancing down at Willie, who was squalling VERY angrily about being splayed uncomfortably over his collar, he figured he'd better stick with first things first.

His first search term, typed with one hand, was "Holding techniques for eight-month-old children."

Apparently, Google was more interested in 'child development' and what the babies _themselves_ could hold at eight months, not the far more obvious subject of how caretakers could hold on to them.

He tried a more generic search term: "How to hold a baby."

He had to turn up the volume on an "Infant Care" YouTube video all the way to hear it over Willie's squalling. She was starting to get sweaty and drooling against his clothes, and he wondered if it were easier for babies to get overheated than humans. Perhaps he could give her some water—but did babies drink water or just milk?

Within a few minutes, however, Sherlock was fully practiced up on the 'chest-to-chest', 'stomach-to-stomach', 'cradle', 'football', and 'lap' holds, Willie being the willing participant for said practicing as he kept his eyes glued to the screen.

He then remembered Mary's instructions and glanced at the clock. It was one-thirty; which meant Willie would need a bottle at four-thirty, unless Mary had already fed her, in which case—

Trying not to alarm himself even more, he quickly turned back to the screen. "Can babies drink water?" was the next search term he typed in.

The general results described consequences of giving water to babies younger than six months as "possible seizures, coma, loss of electrolytes, etc." Sherlock glanced down at Willie again and decided that the two-month age difference was negligible when it came to those kinds of symptoms. He would definitely stick to the bottles.

Next question: "How do you know when a baby should be given a bottle?"

He scrolled through a whole page of information until he got to a source that looked at least somewhat scientific. He read through more information on breastfeeding than he'd seen in his life (and it wasn't the first time he'd researched the topic) before coming to the bottle section. _"The number of times an infant should be bottle-fed varies widely."_

He glared darkly at the screen.

"HOW DO YOU GET A BABY TO STOP CRYING?!"

Google suggesting tacking on, "when babysitting," so he added that, too. After all, he was 98% sure Willie was only upset because Sherlock wasn't her mummy.

When he was done, he carefully stood up, shifting her weight in his increasingly aching arms, and making his way over to the diaper bag. There were THREE bottles in there. Nine hours, right? How long was Mary planning on being gone?

He tried to think. Willie couldn't verbally tell him if she was hungry. Should he wave a bottle in front of her face and see if she responded? Her dark blue eyes lit up wide when she saw the nipple and she quieted for a few seconds, but almost immediately started wailing again.

Sherlock groaned and headed to the fridge to dispense the first two bottles (carefully ensuring Willie didn't see the appendages trailing out of a Styrofoam cup on the top shelf, because that would be irresponsible), then sat in his armchair and attempted to give the bottle to the child.

Eagerly, she leaned in to suck it, took two sips, and burst out crying again, great fat tears rolling down her pudgy little cheeks.

"Oh, why can't anything be logical with you?" Sherlock exclaimed, leaning his head over the back of the chair. "Either you're hungry and you drink it, or you're not and you don't! There's no point in crying about it!"

For the next twenty minutes, Sherlock attempted every infant consolation technique he could think of or find on the Internet. He tried pulling funny faces, he tried checking her diaper (that one would go his list of BIG favors Mary owed him), he made an attempt to sing lullabies, he tried teaching her to recognize photos of famous criminals, he tried propping her up on the couch and imitating every vocal-like sound she uttered on his violin, and even tried ignoring the crying completely and taking a phone call from Lestrade.

THAT was his most terrible idea yet, because his excuses for the background noise soon ran out and Lestrade absolutely flipped out when he heard the truth, letting him off saying he wanted no part in the matter because Sherlock caring for a small child was certain to end in DISASTER!

Finally, Sherlock did the unthinkable.

Tentatively, he raised the phone to his ear and waited for the dial tone to stop.

"Hello? Sherlock?"

"Mummy? Mummy, I need immediate assistance; DON'T tell Dad. Or Mycroft."

"Sherlock, listen, tell your brother to phone me immediately. He's had me hunting around the whole house for his umbrella, but I think it's a ruse because I can't find it anywhere. Tell him the next time he wants to express his frustrations to tell me to my face, or I'll s—"

"Mummy, just because we both live in London doesn't mean we actually _talk_ to each another," Sherlock interrupted impatiently. "Now, help me and my weeping namesake before she cries into a conniption!"

"Are you—" Violet Holmes started. "Is that a baby? Tomas, Sherlock is _babysitting_! Not very successfully, I'm afraid, but did you ever think—"

"Mummy!" Sherlock snapped. "Just tell me—please, tell me—that I was clever enough at eight months not to cry without purpose for hours on end?"

"Oh, heavens no, dear, you were like a tiny-pink version of a werewolf, now, don't get me started. One minute you'd be larky, and the next, I thought your voice would break the cabinet windows!"

Sherlock hung his head desperately.

"…and then, Daddy would hold those stupid glasses of his, and let you play with them, and I thought you would chew on them and hurt yourself but it didn't help either—"

"HOW DO I MAKE IT STOP?!" he bellowed into the receiver.

" _Try using one of those rice-bag things, and warming it up,"_ Sherlock could hear his father call from his chair.

"Oh, don't be ridiculous," Violet responded, "the poor little thing's only eight months! She'd choke if it got under her head—and Sherlock would make it too hot or not warm enough besides."

Sherlock's eyes glazed over as he listened to their bantering, his head starting to hurt from the constant crying in his left ear.

"Did you warm up her bottle when you gave it to her?" Violet's voice returned after a few moments.

"I was supposed to?" Sherlock griped, juggling the bottle he'd pulled from the fridge with the phone and the baby.

"Yes, just pop it in a saucepan for a few minutes. With water, Sherlock, or else it'll melt."

" _Just don't stick it in the microwave! What a disaster that would be,"_ laughed Tomas, again from the armchair.

"Oh, no, certainly don't stick it in the microwave. Remember when Kels did that by accident? Oh, and do you remember that other time with the microwaveable vitamin-packs?" the two began laughing uproariously on the other end.

"Fine. I'll try that!" Not amused, Sherlock shouted into the receiver so they would hear. He pressed the button to end the call—and dropped his phone on the hardwood, cracking the top of the screen.

Sherlock bit his lip, having to suppress a serious urge to scream like a little child. Slowly, he took a deep breath, trying to use his mind palace to temporarily imagine he was somewhere without any crying babies—perhaps a crime scene—even the sniveling relatives of a victim would be preferable to the outright wailing of an infant.

With a huge sigh, he readjusted her on his shoulder so she was better positioned, headed to the kitchen, and turned on the stove, grabbing a panful of water to heat the milk in.

Without warning, Willie flopped over and launched out of his arms toward the hot stove.

"Wil—!" he gasped her name, swinging them both around to avoid her colliding with the stove. The pan clattered to the floor, knocking one of his experiments to the ground in shattered glass and chemicals, spilling everywhere besides.

Shaking, he grabbed Willie from under her arms and held her up to be certain she was all right, looking over every inch of fat baby skin before he was satisfied she hadn't been burned at all.

Suddenly he realized.

 _She had stopped crying._

She had actually stopped crying.

"That—that doesn't make any sense _whatsoever_!" he exploded. "You almost got burned! By a stove! It's the first time you've had a reason to be crying this _whole day_! Why stop now?"

She only giggled in response. Flabbergasted, he carried her back into the living room, determined to figure this out. Her giggles grew more infectious, and Sherlock got the feeling she was laughing at him.

"I've not got the slightest idea why you're doing that, but I'm very, very glad you are," he chuckled, finally collapsing on the sofa, giving her a friendly poke and evoking another convulsive baby laugh.

For a second, he settled her on his lap and just let go of her, letting her clumsily attempt to grab his coat and climb up the front of him. "Remind me to tell your mother I'm never going to babysit again," he scolded. She looked up at him with an inquisitive, innocent look in her blue eyes. "Or—perhaps," he grinned, "just by consultation only."


	2. Chapter 2

**A/N: Thank you all for the kind reviews! The crossover part begins in this chapter, and the Doctor will finally appear with the fabulous Donna Noble in the last part! (It's a 3-chapter story). Thanks, have a fantastic day or night, and please review! I still do not own the fandoms.**

 **FantasticFoe: Thank you! I try to update something every Friday night. Next Friday will be the last chapter for this story.**

 **ThePro-LifeCatholic: Aw, thanks! Sherlock is ridiculously hard to write. I think I'm kind of using him as a segway toward writing Ninth Doctor fics, since Nine is probably the hardest character I've ever tried. Haha. The Doctor appears in the final chapter of this story, though!**

 **thegirlwhoneverforgot: Awesome, thank you! btw I have a story (or two!) that I want to add to the community you made. Do you want to take a look at them first? Just let me know! (:**

Chapter 2

"Come in, come in, have a seat; make yourselves at home, et cetera," Sherlock spouted from memory as he ushered his clients into the flat.

Willie stared inquisitively at them with her wide blue eyes as her uncle held her casually in one arm.

"Thanks, Mr. 'Olmes," the old man replied, shaking his free hand warmly as he stepped inside. The middle-aged woman with him shook hands as well, though in a jerky, nervous manner before taking a seat.

Sherlock watched their movements keenly. The old man affectionately adjusted the couch pillow behind the blond woman's back, but she ignored the gesture, shooting him a look of insolence when he gave it one too many adjusting pats. Clearly, they were father and daughter.

"We didn't know who else to come to, you see," the old man addressed Sherlock after sitting back himself. "We were hopin' you could help us with a missing person? Dy'a do that sort of thing?"

Sherlock wordlessly took a seat with Willie, in his armchair, and settled himself comfortably.

"I told him it wasn't anywhere on your website that you did such things, and that we should've gone to the police, but he insisted that we come here instead, so I do apologize for wasting your time," the woman added, directing a cold stare toward the man beside her.

"Oh, not to worry, Mrs. Noble, I've solved…nineteen…twenty? Missing person cases so far and I _will_ solve yours, provided you give me the right information." Sherlock flashed her his best fake smile.

She started. "Oh, see, that's why I said, too, remember?" she backtracked, nudging the older man, who just rolled his eyes and waited for her to stop. "I said, we never know, so we might as well ask him anyway, just to be—"

"Madam, if you would kindly allow your father to speak," Sherlock sighed, shifting the baby's weight in his arms.

She started again, staring at him as if he were a foreigner. "How did you know he was my dad? We haven't introduced—"

"Never mind that. The case?" he barked impatiently.

"Oh, yes, right t—"

"Your _father_ was speaking?"

The old man was suppressing a grin. "Right!" he began, when the woman finally shut up. "Well, you see, we've got this girl, Mr. Holmes, bright red-headed thing, she's my granddaughter and Sylvia's daughter, and she's the most important thing in the world to us. She ran off with this man, he's called the Doctor, and we try to call her but we haven't heard from her."

"How long ago was this?"

Sylvia started to speak, but with a glance from Sherlock she stopped and the old man continued uninterrupted. "Oh, it was ever since that incident with those little fat people, you know. The ones who got transported up into an alien ship? Wish I'd have seen it," he added, muttering to himself. "It would've been brilliant to see some real aliens, after all these years."

"Ah, yes," Sherlock remembered. "The adipose creatures found walking the streets of London two and a half months ago. I heard of the incident. But why tell me that instead of 'two and a half months'? Did this have something to do with her disappearance?"

"Well, yes…" Sylvia began.

"I didn't even see them," her father added, still remorsefully shaking his head.

"I'm really very worried you see…"

"All them aliens in one night and I didn't even see a one!"

"Mr. Holmes," Sylvia burst out at last, her hands shaking in her lap for worry, "I'm afraid my daughter has been kidnapped—by terrorists!"

Sherlock started laughing, a deep chuckle back in his throat. "No, it wasn't terrorists," he reassured her immediately, as she glared at him. "Why does everyone always think of terrorists?" he added to himself, trying to suppress a smile, which John surely would've scolded him for.

"Oh, don't worry so much, Sweetheart, it's pretty plain that the Doctor's another one of them aliens. You even saw them," the old man kept on. "That's who Donna's with. We're just trying to find out if she's coming back, that's all!"

"Well, it's just—" Sylvia started. Noticing the two men both staring at her. "Well, I don't know, it's just—all these aliens and Donna with them? In the sky? It's impossible," she confessed.

Sherlock smiled slightly. "Once you eliminate the impossible," he said slowly, "whatever is left, however improbable, must be true. Mrs. Noble, given the obvious existence of aliens as you yourself have apparently been a witness, are you certain that your daughter being with an alien is completely, beyond a shadow of a doubt, _impossible_?"

Sylvia opened her mouth, looking as though she wanted to argue but couldn't quite believe what the venerable detective had just said. She made a little, startled-sounding noise, then turned and elbowed her father. "Dad! Did you hear what he just said!" she hissed, sounding shocked.

Her father simply grinned. "That's exactly what I said! I said I saw them in that little blue box, didn't you believe me?"

"All of this is beside the point," Sylvia exclaimed in a huff. "Mr. Holmes, what I really want to know is, is my daughter _safe_? Is she happy? Is she—is she still going to come back, and when? She has a life here! She was going to get a _job_!" she wrung her hands, sounding on the verge of tears.

Sherlock smiled slightly. Willie was asleep now, her tiny head resting against his shoulder. He carefully adjusted his holding position so as not to wake her up. Neither of his guests had said anything about her so far, so he must not have looked too out-of-place with the infant. Perhaps he was getting used to this babysitting practice.

"The answer, Mrs. Noble," he began dramatically, "is this. Your feisty, ginger-haired, travel-addicted, small-necked and in all respects MARVELOUS daughter who likes purple nail polish and Listerine, has a troublesome case of repressed sensitivity, and is slightly prone to temper tantrums," he refused to grin at the open-mouthed expression the mother was now giving him— "is perfectly all right and will be returning home within a few hours, around the time of another major alien disaster, probably one involving _clones_ of some sort... She has never been happier to be away from her nagging mother in all her life and has, frankly, grown a bit more fond of you in her absence, though may I emphasize, a BIT. She has no thoughts of returning as of yet but, as I said before, she is soon to do so anyway and will enjoy her very short stay in your home. Be sure and text me when she arrives. I have a particular interest in meeting this 'Doctor'. Out you go! –I mean, have a wonderful day!"

With that, he carefully lifted the sleeping baby and escorted the father (who was so happy at the news about Donna that he was nearly dancing his way out the door) and his still-open-mouthed daughter (who was making little shocked squeaking noises every couple of seconds) to the stairs, shutting the door behind them.

He sighed in satisfaction as he watched them go. One of the most interesting cases he'd ever had, yet, disappointingly, it was over so quickly.

He made Willie a makeshift bed on the floor with some blankets (the idea again, courtesy of the Internet). He found himself, however, returning to the windows multiple times to check if Mary's car had parked outside the flat. Time and time again, the side street was always empty.

He worked on some experiments (ones that did not involve hazardous chemicals, because Willie must NOT be allowed to breathe those into her tiny, delicate lungs), heated up some leftovers of a dish Mrs. Hudson had made a few days ago, and checked the clock again. It was already 7:06. Willie woke up and he gave her a bottle (he was quite the expert at baby-feeding by now), let her play on the floor with a plastic cup and a soft-edged ladies' pocket mirror he had acquired on an important case, and busied himself checking his emails until Willie fell asleep again at 8:32.

He began to worry as the hands on the clock swung 'round and the street outside began to grow dark. After his experiments were concluded, he proceeded to watch Willie, sleeping in her makeshift bed.

Her face was so unlike his, when he looked in the mirror.

So peaceful, and sweet.

Surely John and Mary would not have left their precious girl with a potential-energy disaster like him, for this long, without a good reason.

Finally, he told himself that worrying would do no good. Perhaps he could treat it like a case.

" _The most perplexing cases usually have the simplest explanations,"_ he reminded himself. Mentally, he sorted through the possibilities and looked for simple ideas.

Perhaps John really WAS ill.

That was—that was not even something Sherlock would think about. John couldn't BE ill, at least not seriously. There were hundreds of other possibilities, besides.

There was a social event, perhaps. Maybe one or more of John's less-than-deserving family members had suddenly died and they were attending the funeral. Maybe a so-called 'friend' of high social status was hosting a party, or a fundraising dinner, or being married.

Yes, that was likely.

Sherlock bit his lip and slung his lanky frame over the couch, twirling a cigarette (before remembering that it wouldn't be good for Willie and switching it for another handful of nicotine patches).

He was about to retreat into his mind palace to do some organizing when he recognized a funny smell in the room. His eyes popped open again.

As Mrs. Hudson frequently reminded him, funny smells were usually not good.

Sure enough, there was a cloudy sort of gas coming underneath the door, and more of it seeping in around the cracks in the windows!

Sherlock leapt to his feet. Someone was trying to gas them out.

" _Moriarty? A cohort of Magnusson's? Black Lotus?"_

It didn't matter. Another sniff told him the exact potency of the gas, and that once it filled the flat, they would have a maximum of eleven minutes before losing consciousness. Willie would probably have less.

He also noticed it smelled very similar to—car exhaust.

" _Carbon monoxide, hydrocarbon, nitrogen oxide…where's it coming from and why is there so much of it?"_

He ran to where Willie was sleeping on the floor. She blinked sleepily and started crying as he picked her up, along with his cracked phone, and ran to the back bedroom where he'd stored some surgical masks for working with vaporizing chemicals.

Strapping one over Willie's face (it completely covered her eyes and forehead) and one over his own nose and mouth, he ran downstairs.

"Mrs. Hudson?" he shouted, trying not to breathe in more of the gas.

When there was no answer, Sherlock mentally kicked himself. Of course she was still out with her—whoever it was she was out with. He dialed John. It rang and rang, but no answer. Then Mary, but the same result—only voicemail, which he didn't wait long enough to listen to.

His mind quickly catalogued recent events—the call that had come that afternoon, Mary dropping off Willie, the adventure with the stove, the clients. What had he told them? There would be a major alien disaster? Had he just assumed said disaster wouldn't affect them at Baker Street?

" _Stupid, stupid, stupid!"_ He wouldn't be making that mistake again.

He ran to the window. Civilians were running, coughing and screaming, away from their cars and into the houses, holding handkerchiefs and bags over their faces to avoid breathing in the gas. The fumes appeared to be coming from the ATMOS systems underneath the vehicles parked outside—hmm, interesting.

His final bit of research consisted of checking the news report on his phone. "WORLDWIDE GAS FLOOD CHOKES INDUSTRIAL CITIES. WILL THIS BE THE END OF THE HUMAN RACE?"

" _None of my concern",_ was his first thought, as he rolled his eyes. Negotiations and political problems regarding aliens weren't exactly his forte. Ask him to locate an alien being or lone agent? Another matter entirely!

Sherlock shook his head. He couldn't exactly save the entire world. But he could save himself and Willie, even if he only had minutes to do it.

Baby in arm, he sprinted up the stairs three at a time, slamming the door shut behind him. The fumes had already reached higher than the flat, so there would be no benefit in getting up onto the roof.

He hastily stuffed Mrs. Hudson's holiday table runner under the door, blocking the fumes partially, and plopped Willie down in a closet with more stuffing under the door. That would at least give her a little more time.

He dramatically swiped out the whole table of experiments, letting the materials crash to the floor unnoticed.

" _Gas sample."_

He grabbed his supercooling solution in its convenient aerosol can. It had been a gift from Molly and treated with a significantly greater level of affection.

If he'd been more sentimental, he might've vowed to treat her more nicely, if he ever got out of this alive.

Quickly, he sprayed a thick cloud, condensing a few drops of gas into a liquid onto a spot plate.

" _Six minutes left."_

One solution in each drop of condensed gas…His eyelids were already beginning to droop…He had a suspicion the poison would be neutralized with cuprous chloride and one other chemical. There were many solutions that could possibly work, but ammonia seemed like the best bet.  
With those two chemicals, he had the carbon monoxide neutralized, however, the gas wasn't straight car exhaust. There were a few other chemicals he wasn't quite sure how to neutralize.

" _Five minutes."_

He spotted another drop with the remaining ingredients to absorb the hydrocarbons. What else was it that he needed? He desperately hoped it wasn't some sort of alien compound. In all likelihood no chemical on Earth could absorb a foreign chemical.

" _Four minutes."_

"Think, think, think, think, THINK!" He gagged on the fumes as they started to grow more concentrated in the room. His vision grew spotty and for a second he just wanted to collapse on the floor and _sleeeeeep_.

" _Three."_

Whether it was a hallucination or just a memory, he didn't know, but he thought he saw Willie smiling at him, gurgling happily like she had earlier that day.

Sherlock had never been given charge of her, although he'd always loved her, since the day he shot Magnussen to ensure she would have a childhood, and that other day when he'd held her beside Mary's bed, fresh from the womb.

Her first time in his charge would be the last time.

She was dying.

John's baby couldn't DIE.

It wasn't even an option.

John's baby WOULDN'T die, not when Sherlock Holmes was around to save her!

" _Two."_

Out of the fogginess of his blackening brain, he had an idea.

The additional chemical wasn't being absorbed by the current ingredients, but perhaps it would be if its current state was altered. He'd condensed the gas so he could work with it at the table, but what if he already had the solution right? What if the reason it wasn't absorbing the condensed gas was because it wasn't actually in its gas state?

Willie had refused her bottle earlier. It had been too cold.

The gas was refusing the neutralizers because they were too cold. The additional elements, surely, were only altered versions of Earth's, only adjusted to different climates.

He had to heat up the neutralizer and feed it to the gas, just like a warm bottle.

Ugh. " _So domestic."_

" _One."_

He stumbled over to the stove and turned all the burners up on full heat. Rapidly, he combined all of his final solution, hoping some of the labels were right because he was nearly unconscious and finding most of the ingredients by location only as his vision grew spotted.

He swirled it all around in the biggest Erlenmeyer flask he owned, waved his hand over the stove to make sure it was hot enough, and poured a stream of liquid onto the hot surface.

 _Zero._

A huge cloud of steam billowed up, and only falling to the floor unconscious saved him from a serious burn as it rose and filled the room.


	3. Chapter 3

**A/N: The Tardis arrives! And the story is complete! Thank you to everyone who enjoyed this story and left me some feedback! Once again, I do not own "The Sontaran Strategem", "The Poison Sky", or Sherlock Holmes, no matter how out-of-character I write him.**

Chapter 3

When Sherlock woke up, it was to a strange, " _VWOOORRPP! VWOOORRPP!"_ sound, and a rush of air that was filling the now gas-free room. Blearily, he lifted his aching head from the floor. He was covered in the sticky remains of the various chemicals he'd used. Fortunately, once it had combined with the gas, it was neutralized and therefore he didn't feel like his skin was being charred into burnt flakes of organic matter.

Slowly, he picked himself off the floor, staring hard as he noticed a fuzzy shape of a blue box coming into view in tempo with the _"VWOOORRPP!"_ sound. It looked like something from the telly, not something that should be appearing out of nowhere before his eyes.

What was it that made it do that? Quantum teleportation on a massive scale, combined with metamaterial wood, perhaps?

Within a few more seconds, the entire structure had taken shape in his sitting room. Sherlock stumbled around to where it sat, quietly, as if a police box sitting in one's sitting room was the most normal thing in the world.

A tiny smile graced his lips.

The door suddenly flew open and a spectacled man with spiked hair that looked as though it belonged on the telly equally beside his wooden box bounded from the inside.

Sherlock quickly found it was more difficult than he'd thought to deduce anything about him. Clearly he was not from this world—he hypothesized that this was possibly an alien who had brought about the corruption of ATMOS and the poisonous gas? But he didn't possess any soldier's bearing, which was strange because his jerking movements clearly told of suppressed emotion one might readily associate with battle experience.

The stranger grinned wildly, quickly hopping out of the box and experimenting with the cushioning level of Sherlock's carpeting with his converse. "Ah, hello! You must be Sherlock—the famous Sherlock Holmes, I'm assuming." he extended his hand and shook Sherlock's by rapidly pumping it up and down. "Oooh, you look like you've been in a bit of a bad way. Hope that didn't have anything to do with the gas, and the Sontarans, and all that. I've just been busy taking care of it, if you don't mind."

"Why—why would I mind?" Sherlock's eyebrows creased.

The Doctor slung an arm around his shoulder like they were pals from—football—or interns—or something. "Well, you see, thing is, your friends look just as disheveled as you are at the moment. I told them to get cleaned up in the Tardis—that's my Tardis, you see," he continued with a grin, pointing to the blue box, "She's a—complicated thing that travels in time and space—and I told them to get cleaned up, but I think they're a little too busy TOUCHING every little thing they see!" he yelled pointedly toward the inside.

When there was no response, the Doctor simply rolled his eyes and grinned at Sherlock. "I don't mind it, though. They're nosy, and I like nosy people. I hear you're a bit of a nosy person yourself! Too bad you had to miss out on our last adventure! Although I wouldn't doubt being in charge of a human spawn was more than enough adventure for you, eh, Mr. Detective?"

"John and Mary have been in that box with you the entire time they've been gone?" Sherlock demanded, a little angrier than he'd intended to be.

"Oh, no," the Doctor rambled on happily, "They've been saving the Earth with me. Big old Sontaran ship—the Sontarans are the great warriors of the universe, never back away from a fight—trying to convert the planet into a cloning world! Clone soup! All that gas? It was meant to be fed to the clones!"

Sherlock blinked. "Like a baby's bottle?"

"Ehhh—yeah, I guess you could say that, why?"

"Oh, no reason, no reason at all. Speaking of which, if Mary asks, I did NOT forget and leave the baby in the closet…" he suddenly remembered.

"Didn't forget what?" a flushed, angry-looking Mary appeared in the doorway of the box.

"Oh! That I took extremely good care of your daughter while you were away and didn't let her get splashed by any of my experiments or take her to any crime scenes." Sherlock summed up quickly, stopping just outside of the closet, through which a (thankfully) healthy-sounding baby cry could be heard.

"Oh my gosh, my poor baby," Mary moaned upon hearing the noise, pushing through to get to the closet. She opened the door, scooped her up off the floor and held her closely, making ridiculous baby sounds and giving her repeated kisses.

John was out of the box right behind his wife. "Why's she wearing a surgical mask?" he asked, confusedly.

"Actually use your brain for once, John, and it will come to you presently," Sherlock replied dryly.

"Oh, the gas!"

"Brilliant deduction."

"Ah, there she is," the Doctor grinned upon seeing Willie for the first time. "The most brilliant Watson of all the brilliant Watsons! You're going to be a real shock to your parents as you get older, you know that?"

"Wait, how do you know that?" John questioned.

Sherlock tried to interject.

"I speak baby," the Doctor replied nonchalantly.

Sherlock tried again.

"Although, strictly speaking of course, there are several major dialects chiefly evolving from the prenatal exposure to different types of radioactive myochlorabineate particles…"

"What the heck are myochlorabineate particles?" Sherlock stopped whatever he was trying to say for a moment to ask the more important question.

"Subset of quarks and radiation compounds. Science'll catch up to it in, oh, about eighteen years? You've got a lot to look forward to as a chemist in the near future," the Doctor waggled his eyebrows.

Sherlock cleared his throat rather loudly. "What I was _attempting_ to say earlier was—where on Earth is your companion, Doctor? The feisty ginger two of my clients came and asked me about."

"Oh, you mean Donna! I love Donna; what a dear," Mary interjected, smiling as she held the now much happier-looking baby in her arms.

"Truly marvelous, that woman," John added. "It's not often you meet the likes of her."

"Donna?!" the Doctor yelled inside the Tardis, impatiently banging on the door. The ginger still hadn't shown her face outside. A voice, however, could be heard, sounding muffled from the interior.

"Oi, don't rush me on like I'm your pet dog or something," her head suddenly appeared from around the doorway. "I was in the loo, you idiot. Surely I'm not the first companion you've had that has to use the loo on occasion?"

Sherlock smiled in spite of himself. Donna Noble was, in fact, exactly as he had described to her mother and grandfather, and that made him rather proud of his accomplishment.

The Doctor made a face. "Right, sorry. Anyway, this is Donna, Sherlock, Willie. Well, we'd best be off. We're on our way to say good-bye to Martha, since she demanded we come back before we leave Earth again. Not that it's so incredibly hard to come back at a better time," he added in a grumbling tone, and Donna gave him a reproachful look.

"It was good to meet you, Doctor," John shook his hand heartily. "You too, Donna."

"Look after yourselves, both of you," Mary smiled, giving them both a good, strong hug. "Don't fly too far. You've got to come back and visit sometime."

"You might want to have consulted me on that first," Sherlock "harrumphed!" under his breath, and John gave him a confused look.

"Good luck, all of you! Keep up with your chemistry, Sherlock. You might save the universe with it sometime in the future!" the Doctor waved merrily before stepping back inside the box and running up to the controls.

"See you all later!" Donna shouted and waved before shutting the door to the box.

"Good-bye!" John and Mary called, as the baby cooed loudly and Sherlock merely waved in a cordial fashion.

The _"WHOOSH!"_ filled the room again, blustering Sherlock's papers all about the floor and the table, and the light on the top of the box began to flash as it slowly disappeared from sight with a _"VWWOORRPP! VWOOORRRPP! VWOORRPP! VWORP! VWORP! Vworp! Vworp. Whoosh!"_

The flat was as quiet as it had been before the box had ever arrived.

Willie started crying again.

Mary turned to her husband's best friend. "So, Sherlock, how did it go?"

 _Sherlock! BBsitter needed 4 tonite! REALLY need one bad. 5:00?_ –Mary

 _Mary, for the last time, I am not your private babysitter_. –SH

 _im not saying that! I just rlly need 1 4 tonite! Like I already said!—_ Mary

 _PLEEEEESE_ —Mary

 _Sherlock im begging you_ —Mary

 _I babysit by consultation only._ –SH

 _I'm consulting you.—_ Mary

 _Understand that monitoring the wellbeing of a human infant is an incredibly complex task that requires some preparation beforehand._ –SH

 _meaning?—_ Mary

 _Meaning there may be some articles around the flat that are not suitable for children to see_. –SH

 _still, meaning?—_ Mary

 _A head floating in a jar, for instance._ –SH

 _She's 8 mos.! she'll think it's a plaything!—_ Mary

 _It has one eye gouged out and the rest of the face has been maimed and scarred with a jagged knife_. –SH

 _ok mab u have a point._ –Mary

 _Honestly Mary, I think sometimes I'm better at this than you are_. –SH

 _Don't even go there. You won't even agree to babysit._ –Mary

 _Fine. I will babysit tonight. But I am a consulting babysitter, not a private nanny.—_ SH

 _Mary? Did you understand me very clearly?_ –SH

 _Mary?_ –SH

THE END


End file.
